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Abstract. Junctional coupling was assessed during the transition from the fourth to the fifth cell cycle of mouse embryogenesis by injection of the dye carboxyfluorescein and by measurement of electrical continuity between cells. Junctional coupling, which arises de novo in early 8-cell mouse embryos, subsequently becomes reduced towards the end of the cell cycle as the blastomeres enter into mitosis. Arrest of the cell cycle in metaphase by nocodazole, an inhibitor of tubulin polymerization, reveals that cell coupling becomes undetectable at mitosis. Junctional coupling then is resumed during interphase of the 16-cell stage. Nocodazole itself has no effect on junctional coupling in interphase cells, regardless of the extent of intercellular flattening, whereas taxol, a microtubule-stabilizing agent, does reduce the extent of coupling in interphase cells.

Chemical constituents of fasting vuine-Continued. Phosphorus Sulphur Total acidity /S-oxybutyric acid Mineral metabolism Relationships of the mineral constituents Reducing power Carbon in uiine Carbon-nitrogen ratio Energy of urine Calorie-nitrogen ratio Calorie-carbon ratio Microscopy of urine and tests for albumin Detailed results Summary The respiratory exchange Apparatus and methods used in the calorimeter experiments Absorption of water-vapor and carbon dioxide Analysis of chamber air at the end of periods Tension equalizer Argon in oxygen from liquid air Graphic registration of degree of muscular repose of subject inside the respiration calorimeter Methods used in experiments with the respiration apparatus Studies with the bed calorimeter Atmospheric conditions inside the chamber Measurement of the respiratory exchange inside the bed calorimeter Periodic changes in the metabohsm Total metabohsm Respiratory quotient Relationships of pulse-rate, body-temperature, and metabolism Studies with the universal respiration apparatus Variations in the metabolism as the fast progressed Relationship between the pulse-rate and the metabohsm Diurnal variations in metabohsm External influences upon metabolism Effect of changes in body position Influence of the work of writing Influence of breathing an oxygen-rich atmosphere 1 Influence of sleep Metabolism per unit of weight and surface Metabohsm per kilogram of body-weight Metabohsm per kilogram of body-weight in calorimeter experiments . . Metabohsm per Mlogram of body-weight in respiration-apparatus experiments 362 Conclusions regarding the metabolism per kilogram of body-weight . . . Metabohsm per square meter of body-surface Metabolism per square meter of body-surface in the calorimeter experiments 369 Metabohsm per square meter of body-surface in the respiiation-appatus experiments 370 Conclusions regarding the metabohsm per square meter of body-surface . Summary of results regarding the metabohsm per kilogram of body-weight and per square meter of body-surface Elimination of water through limgs and skin Calorimetty 379 Direct calorimetry 379 Indirect calorimetry 384 Balance of income and outgo 392 Total katabohsm per 24 hours 392 Daily activity 393 Total carbon-dioxide production and oxygen consumption per 24 hours ....

Human Y-bearing spermatozoa, as identified by the quinacrine staining technique, were found to be significantly more motile than X-bearing spermatozoa under laboratory conditions. This difference is consistent with current estimates of the difference in mean head DNA content.It has often been surmised that male-determining Y-chromosome bearing spermatozoa may differ in some respects from female-determining X-bearing spermatozoa. Although early attempts to separate the two kinds on the basis of supposed differences in mass, density or surface charge met with little apparent success (Beatty, 1970), the recently developed quinacrine technique for detecting the human Y chromosome in spermatozoa (Barlow & Vosa, 1970; Sumner, Robinson & Evans, 1971) now enables these possibilities to be investigated without the necessity for experiments involving insemination. Results have been obtained which suggest that Y spermatozoa may be more motile than X spermatozoa (Rohde, Portsmann & Dörner, 1973; Ericsson, Langevin & Nishino, 1973), although the results of Ericsson et al are not confirmed by others (Evans, Douglas & Renton, 1975; Ross, Robinson & Evans, 1975). We describe here an experiment, based on the quinacrine staining method, which was designed to detect possible differences in motility between the two types of spermatozoon. Motile spermatozoa were layered at the bottom of a vertical column of fluid and were then allowed to swim upwards into the medium. If Y spermatozoa are more motile then they should outnumber X spermatozoa in the upper regions of the column (Roberts, 1972). This system possesses two useful features; firstly, equilibrium is eventually reached in which the numbers of organisms at given heights show no further changes, which simplifies the experimental procedures involved, and secondly, the degree of separation obtained can be used to estimate the difference in motility between X and Y spermatozoa. Methods and resultsSemen was provided by volunteer donors and used within 2-3 hr. Each sample was diluted to 10 ml with warmed Tyrode's solution (pH 7-8) and centrifuged at 1000 g for 15 min. The pellet was resuspended in 5% bovine serum albumin (25% BSA in Tyrode's solution (Sigma) diluted with Tyrode's solution to 5 % final concentration), the final sperm concentration being about 5 107 ml-1 as determined by haemocytometer. A portion of this suspension was set aside as a control. Experi¬ ments were performed on columns 18 mm in total height, each of which comprised a cylindrical portion of 21 mm diameter and 10 mm height and an upper conical portion of 8 mm height through the apex of which the contents of the column could be expelled. The columns consisted of Tyrode's solution stabilized with a BSA gradient, varying continuously from 0-2% at the top to 2-0% at the bottom, which was delivered from a small two-compartment gradient former. A suspension contain¬ ing about 5 106 spermatozoa was introduced through a side port at the bottom of the column as a layer 300 µ thick. After 1 hr, when spermatozoa had dis...

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